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Topic Review (Newest First)

01-30-2007 11:19 AM

70bird

Please, check the date of the last response before posting. This post has been dead for 2 years and 2 days.

01-30-2007 10:16 AM

shiftstick

RE:Vacuum Adv

Malc, Read the reply that (Triaged Posted) this is the information you and the others need to understand to get the correct timing. I will add to the post by saying this. Initial timming is just THAT initial timming. it is also called static timming and is used as the base line to get the remaing timing required to get the engine running properly. The initial timing for the SBC is generaly 8-12 degrees BTC NOTE! this will get the engine started. If you do not have a vacuum advance dist.you will have to advance the dist timming to some where in the mid to high teens to smooth out the engine at idle.This is the reason the idle quality will be much better when vacuum is added to the vacuum adv distributor, when vac is applied the ignition will be increased from the 8-12 initial timming setting to a new higher timming degree setting. This amount will vary depending on where the vacuum can is adjusted to. The adjustable vacuum cas will have a hex formed on the can exterior. With the vac hose disconected the vacuum advance can be be adjusted by inserting a allen wrench into the hole in the nipple where the hose connects. With the engine started check initial timming approx 10 deg with timming light.With a vacuum hose connected to full vacuum plug into dist vacuum can and check timming. the timming should be some where in the mid teens I.E. 16-18 degrees. this should produce a decent idle quality (if carb is adjusted). Now check for total advanced timming, this will require about 3000 rpm for most after market dist mechanical advance systems. The timming should be some where around 42 degrees total, this will be a function of Initial timming of 10 deg. +vac adv 8 deg.+ mechanical adv of 24 deg.10 +8 + 24 = 42 total advance. The mechanical advance is limited by the manufacture and generally will be in the 24 -28 degree range and is controled by a stop.This stop can some time be adjusted but usually by 2-4 degrees in most cases. Note total timming is a function of many engine mods. My SBC is set up at 10 initial 8 deg.vac adv and 24 mechanical=42 total . 030 over bore mild cam and Edelbrock 2x4 set up very streetable at 13-14 MPG and low to Mid 12's at the strip. Good luck

01-28-2005 03:31 AM

red65mustang

70 bird

Agree with dmorris, start a new thread, something like "Need help on a Q jet".
Several people who post here are big time Q-jet fans.

OK, group hug....

peace and happyness, dmorris

01-27-2005 04:29 PM

dmorris1200

Did someone say group hug???

01-27-2005 12:46 PM

70bird

lol

01-27-2005 12:21 PM

454C10

Ok.

Time for a group hug.

01-27-2005 11:18 AM

underdog305

No way a good arguement is good for everyone to read. I for one can always learn from two points of view!

01-27-2005 10:39 AM

70bird

You guys need to go to your room (PM) and argue, not out here where everyone else has to hear you.

01-27-2005 10:24 AM

dmorris1200

Re: dmorris,

Quote:

Originally posted by red65mustang from Webster's dictionary

current: a flow of electrical charge

volt: unit of electric potential

Funny that is just what I said. A volt is a measurement of force (also known as potential). Volts are not electrons as you stated. Volts are a measurement of the amount of force or potential that is available to move electrons. That movement is measured in Amperes. Similar relationship would be in a garden hose. There is water pressure which is a force that could propel the water. That pressure or force would be waters voltage (if measured that way). 120psi might be it's pressure or 'voltage'. Until you open the nozzle there is no flow (current). Once the nozzle is opened flow is allowed and you would now have a measurment of how much water is flowing, that would be similar to current flow and measured in Amperes. In an electrical circuit if you measured voltage at a switch that is in the off position you would still see circuit voltage at the 'hot' wire to the switch but untill you close the switch there is no current flow. Voltage present with no current flow. Once you close the switch the circuit is complete and you have current flow (electron flow) which is measured in Amperes. A measurement of potential/force does not actually move or flow it is the electrons that flow and they are measured in Amperes. I don't understand were your comments are coming from but it is getting difficult to not treat you like a complete idiot. Nothing you say makes any sense from one post to the next.

70bird, just a thought. You may be better off starting a new thread so more members might check it out. There may be some members not checking this thread cause it is older.

01-27-2005 10:06 AM

454C10

Sure they go bad and just about anything can stick. Use a timing light to see if that is happening.

If your vacuum advance is on the wrong port then the timing will be very high at idle causing it to diesel at stut down.

It sounds like you need a stronger carb return spring due to wear or corrosion in the carb linkage. Or maybe some carb cleaner on the throttle blades.

01-27-2005 09:49 AM

70bird

I have a situation, that after reading this thread, I think is vacuum advance related.

This is in my 76 K-5 Blazer, stock 350 w/recently rebuilt q-jet. I think I am running ported vacuum. I haven't had time to mess with the ported/full thing. All my free time is going to homework and the Bird.

To get my truck to idle down to around 750-800 rpm, in park, after driving, I have to blip the throttle and that doesn't always work. It usually wants to idle at around 1000-1100 when warm in park. If I shut it down at that rpm it will desel about half the time. If I blip the throttle while in gear before I put it in park, parks idle will be around the desired 750-800 resulting in no desel. A previous q-jet equipped chevy truck I had, had the same problem but not as bad. I used to think this was caused by the q-jet but after learning about vacuum advance and it's affects, I think this may be where the problem lies. Do the vacuum canisters go bad? Could it be sticking, or the diaphram be stiff from old age? For all I know, this may be the original one.

Let me know what you think.

01-27-2005 06:52 AM

red65mustang

great post malc....

does go into the "new" quantum theory answer...there is no answer.

Further to the electron "I am a wave and a particle at the same time"... if an electron was measured to be at point A, they don't know how or what route it took to get to point B when measured. They have proved it's not just moving (as time passes) A to B in a (?) line.

What in the world are the next generation of kids going to have to comprehend!

Atleast the old "water flowing down a hill in a river" didn't give you a headache!